Normal Brain Histology & Basic Neuropathologic Reactions Flashcards
What is unique about the CNS? (3)
Selective vulnerability of neuronal systems
Mature neurons are post-mitotic cells
Unique anatomic/physiologic characteristics
What are some unique anatomic/physiolgic characteristics of the CNS? (6)
- Bony enclosure
- Metabolic substrate requirements (glucose, O2)
- No lymphatic system
- Presence of CSF
- Limited immune surveillance
- Physical barrier – BBB
- Distinctive response to injury & healing (astrocytic reaction)
Normal neurons are integrating & transmitting cells of the CNS, using _______ & _______ means.
Morphology varies by ______.
chemical & electrical
location
What is unique about the nucleus of normal neurons?
- Most have large nucleus w/ prominent nucleolus
- Well-defined cytoplasm containing Nissl substance
- Nissl substance = rER
- Branching processes (dendrites) & longer cell process (axon)
- Axons have terminal synapses for chemical transmission to another neuron
Where are these neurons located?
- Pyramidal & granular neurons
- Betz cells
- Granular neurons
- Purkinje cells
- Anterior horn cells
- Globoid shaped cells
- Melanin containing cells
- Pyramidal & granular neurons
- **Cerebral cortex **
- Betz cells
- **Primary motor cortex **
- Granular neurons
- Hippocampus & cerebellum
- Purkinje cells
- Cerebellum
- Anterior horn cells
- **Spinal cord **
- Globoid shaped cells
- **Deep gray nuclei **
- Basal ganglia, thalamus, brainstem
- Melanin containing cells
- Brainstem
- Substantia nigra, locus ceruleus
What type of cell is this?
Anterior horn cells (motor neuron)
What type of cell is this?
Cerebral cortex neurons
Pyramidal shape
What type of cell is this?
Neuromelanin-containing neurons in brainstem
Substantia nigra, locus ceruleus, motor nucleus of vagus
What type of cell is this?
Granular neurons of the dentate fascia of the hippocampal formation
What type of cell is this?
Purkinje cells & granular cells of the cerebellar cortex
_______ accumulates in neuronal cytoplasm w/ age.
Lipofuscin
Cerebral neocortex (isocortex) contains ____ layers, numbered sequentially from ______ to _______.
6 layers
superficial to deep
What is this?
- Cerebellum
- ML = molecular layer
- PCL = Purkinje cell layer
- GCL = granular cell layer
- WM = white matter
What are the reactions of neurons to injury? (3)
- Eosinophilic changes (ischemia/hypoxia)
- Central chromatolysis (axonal damage)
- Intraneuronal inclusion formation
Eosinophilic Degeneration
Definition
Morphologic criteria
- Indicated lethal ischemia, hypoxia or hypoglycemia
- 12-24 hrs to manifest (light microscope level)
-
Morphologic criteria
- Shrinkage of neuronal cell body
- Loss of Nissl w/ cytoplasmic eosinophilia
- Loss of nucleolus w/ nuclear pyknosis
What is this?
Scattered acutely hypoxic/ischemic neurons
(Eosinophilic Degeneration)
Central Chromatolysis
Definition
Reversible or Irreversible?
Histology
- Manifestation of switch from manufacture of synaptic to structural proteins in response to axonal damage
- Reversible, if axonal repair is successful
- Cellular swelling w/ margination of Nissl substance & nucleus
- Accumulation of filaments & organelles
What are the 2 types of glial cells of the CNS?
-
“Macroglia”
- All derived from neuroectoderm
- 90% of CNS cells
- Astrocytes
- Oligodendrocytes
- Ependymal cells
-
Microglia
- Derived from bone marrow
Astrocytes
Characteristics
Components
- Primary replicating cell w/i CNS
- Round to oval nucleus (10 μm) w/ radiating cytoplasmic processes
- Star-shaped cytoplasm, normally invisible on H&E staining (unless reacting to injury)
- Glial fibrillary acidic protein (GFAP) – major cytoplasmic structural protein
- Ab to GFAP help visualization of astrocytes
Astrocytes
Function (4)
-
Contribute to BBB
- Cytoplasmic processes (end-feet) on blood vessel walls
- Control flow of macromolecules btwn blood, CSF & brain
- Responsible for repair & scar formation
-
Maintain extracellular environment
- Metabolic buffers or detoxifiers & supply nutrients
- Structural support
What are reactive astrocytes?
- Astrocytes activate in response to various pathologic conditions
- Provides evidence of disease process
- Astrocytes divide & become larger
- Increase in GFAP filaments reflected in visible eosinophilic cytoplasm
- GFAP Ab will help identify the reactive astrocytes
- Cytoplasm may appear starlike (fibrillary) or large & round (“gemistocytic”)
Oligodendroglia
Definition
Characteristics
- Responsible for myelination in CNS
- White matter >> gray matter
- Smaller nucleus & fewer processes than astrocytes
- Round dense nucleus
- Peri-nuclear halo (artifact)
- Do NOT synthesize GFAP
- Lethal injury –> demyelination
What are 3 important diseases involving oligodendrocytes?
- Multiple Sclerosis
- Progressive Multifocal Leukoencephalopathy
- Oligodendrogliomas
Ependymal cells (Ependyma)
Characteristics
- Cuboidal to columnar glial ciliated cells that line vestibular surfaces
- Lateral surfaces have cell junctions forming CSF-brain barrier
Choroid Plexus
Characteristics
- Tufts of epithelium projecting into ventricles
- Secrete CSF
- Papillary architecture
- Cell junctions btwn cells ensure CSF-brain barrier
Microglia
Definition
Histology
- Monocyte/macrophage-derived cells that reside in the CNS
- Normally inconspicuous, sparse, rod-shaped nuclei w/o visible cytoplasm
What happens to microglia w/ CNS injury?
With CNS injury, may become activated
- Migrate to site of injury
- Proliferate
- May differentiate into tissue MΦ
- Foamy clear cytoplasm
What happens to microglia w/ viral infections?
HIV?
- In viral infections, astrocytes & microglia form microglia nodules at sites of neuronal injury
- HIV infection stimulates cellular fusion resulting in multinucleated giant cells in microglial nodules
What is the Virchow-Robin space?
What is a Neuropil?
-
Virchow-Robin Space
- Large arteries w/i the subarachnoid space supply the brain by penetrating into the parenchyma
- Initially maintain a perivascular space
-
Neuropil
- Network of dendrites & axons in the gray matter
- In btwn the cell bodies
What are Meningothelial Cells?
- Present throughout the arachnoid membranes covering the brain & spinal cord
